package com.summli.basic.class08;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;

/**
 * 给定一棵二叉树的头节点head，和另外两个节点a和b。
 * 默认a,b在这颗树上
 * 返回a和b的最低公共祖先
 * info：
 * 是否包含 a，是否包含b
 * 公共祖先：
 */
public class Code07_lowestAncestor {

    public static class Node {
        public int value;
        public Node left;
        public Node right;

        public Node(int data) {
            this.value = data;
        }
    }
    public static class Info {
        public Node ans;
        public boolean findO1;
        public boolean findO2;

        public Info(Node ans, boolean findO1, boolean findO2) {
            this.ans = ans;
            this.findO1 = findO1;
            this.findO2 = findO2;
        }
    }
    public static Node lowestAncestor2(Node head, Node o1, Node o2) {
        if(head == null){
            return null;
        }
        return process(head,o1,o2).ans;
    }

    private static Info process(Node head,Node o1,Node o2) {
        if(head == null){
            return new Info(null,false,false);
        }
        Info leftInfo = process(head.left,o1,o2);
        Info rightInfo = process(head.right,o1,o2);

        boolean findO1 = head == o1 || leftInfo.findO1 || rightInfo.findO1;
        boolean findO2 = head == o2 || leftInfo.findO2 || rightInfo.findO2;
        Node ans = null;
        if(leftInfo.ans != null){
            ans = leftInfo.ans;
        }
        if(rightInfo.ans != null){
            ans = rightInfo.ans;
        }
        if(ans == null){
            if(findO1 && findO2){
                ans = head;
            }
        }
        return new Info(ans,findO1,findO2);
    }

    // for test
    public static Node generateRandomBST(int maxLevel, int maxValue) {
        return generate(1, maxLevel, maxValue);
    }

    // for test
    public static Node generate(int level, int maxLevel, int maxValue) {
        if (level > maxLevel || Math.random() < 0.5) {
            return null;
        }
        Node head = new Node((int) (Math.random() * maxValue));
        head.left = generate(level + 1, maxLevel, maxValue);
        head.right = generate(level + 1, maxLevel, maxValue);
        return head;
    }

    // for test
    public static Node pickRandomOne(Node head) {
        if (head == null) {
            return null;
        }
        ArrayList<Node> arr = new ArrayList<>();
        fillPrelist(head, arr);
        int randomIndex = (int) (Math.random() * arr.size());
        return arr.get(randomIndex);
    }

    // for test
    public static void fillPrelist(Node head, ArrayList<Node> arr) {
        if (head == null) {
            return;
        }
        arr.add(head);
        fillPrelist(head.left, arr);
        fillPrelist(head.right, arr);
    }

    public static void main(String[] args) {
        int maxLevel = 4;
        int maxValue = 100;
        int testTimes = 1000000;
        for (int i = 0; i < testTimes; i++) {
            Node head = generateRandomBST(maxLevel, maxValue);
            Node o1 = pickRandomOne(head);
            Node o2 = pickRandomOne(head);
            if (lowestAncestor1(head, o1, o2) != lowestAncestor2(head, o1, o2)) {
                System.out.println("Oops!");
            }
        }
        System.out.println("finish!");
    }
    public static Node lowestAncestor1(Node head, Node o1, Node o2) {
        if (head == null) {
            return null;
        }
        HashMap<Node, Node> parentMap = new HashMap<>();
        parentMap.put(head, null);
        fillParentMap(head, parentMap);
        HashSet<Node> o1Set = new HashSet<>();
        Node cur = o1;
        o1Set.add(cur);
        while (parentMap.get(cur) != null) {
            cur = parentMap.get(cur);
            o1Set.add(cur);
        }
        cur = o2;
        while (!o1Set.contains(cur)) {
            cur = parentMap.get(cur);
        }
        return cur;
    }

    public static void fillParentMap(Node head, HashMap<Node, Node> parentMap) {
        if (head.left != null) {
            parentMap.put(head.left, head);
            fillParentMap(head.left, parentMap);
        }
        if (head.right != null) {
            parentMap.put(head.right, head);
            fillParentMap(head.right, parentMap);
        }
    }
}
